Nuclear physics

Nuclear physics is the study of tiny parts inside atoms called atomic nuclei. It looks at what these nuclei are made of and how they work together. This is different from atomic physics, which studies the whole atom, including the electrons that orbit around it.

Discoveries in nuclear physics have helped create many useful tools and technologies. These include nuclear power plants that make energy, special medical treatments, and imaging machines that help doctors see inside the body. It also helps scientists understand how old things are, like ancient artifacts or rocks, by using a method called radiocarbon dating.

Nuclear physics is also closely linked to particle physics, which studies even smaller parts of matter. When we study how nuclei work, it helps us understand big questions about space, like how stars shine and how the elements that make up our world were created.

History

The history of nuclear physics began with the discovery of radioactivity by Henri Becquerel in 1896. He found that some materials could glow without light. Soon after, J. J. Thomson discovered the electron, showing that atoms have smaller parts inside them.

Scientists kept studying radioactivity and found three types of energy coming from atoms: alpha, beta, and gamma radiation. In 1911, Ernest Rutherford did an experiment where he shot tiny particles at thin gold foil. Most went straight, but a few bounced back sharply. This showed that atoms have a tiny, dense center called the nucleus.

Later, Arthur Eddington suggested that stars shine because of a process called nuclear fusion, where tiny parts called nucleons join together and release energy.

In 1932, James Chadwick discovered the neutron, a tiny particle with no charge. This helped explain how atoms stay together. With this discovery, scientists could better understand how energy is stored in the nucleus.

Hideki Yukawa also helped explain how the nucleus stays together with a force called the strong force. This force works between particles called protons and neutrons.

These discoveries led to many useful tools and technologies, like nuclear power and medical imaging.

Modern nuclear physics

Main articles: Liquid-drop model, Nuclear shell model, and Nuclear structure

A heavy nucleus is made of many tiny parts called nucleons. Scientists think of it like a drop of liquid, where the energy comes from how tightly the parts stick together. This idea helps explain why some nuclei break apart easily.

There are also tiny, invisible rules that change how the nucleus behaves. These rules help explain why certain numbers of neutrons and protons make a nucleus very stable. Scientists study these tiny parts and how they work together in many ways.

Nuclear decay

Main articles: Radioactivity and Valley of stability

Some elements stay the same forever, but many others change over time. These changing elements can turn into different elements in different ways. For example, one type can change by turning a neutron into a proton, creating a new element. Another way is by sending out a tiny piece, which also changes the element. There are even ways where the nucleus sends out energy without changing the element.

Nuclear fusion

In nuclear fusion, two small nuclei come very close together and join. This needs a lot of heat or pressure to happen. When they join, a lot of energy is released. Stars, like our Sun, shine because of this process, turning hydrogen into helium. Scientists are working to use this process to create energy here on Earth.

Nuclear fission

Nuclear fission is when a heavy nucleus breaks into smaller pieces. This can happen naturally or when a nucleus absorbs a neutron and then breaks apart. This process releases a lot of energy and is used in nuclear power plants and some very powerful bombs. Certain heavy elements can break apart on their own, but they more often change in other ways.

Production of "heavy" elements

Main article: nucleosynthesis

After the Big Bang, the universe cooled and simple particles formed. Most of the universe’s helium came from this time. Heavier elements, like carbon and iron, were made inside stars over time. Stars create these elements by joining smaller particles together. The heaviest elements are made in explosions called supernovas, where conditions are just right for adding many neutrons quickly, which then change into new elements.